#include"stdio.h"
int main()
{
	int i,j,f,n;
	double sum,item;
	printf("Enter n:");
	scanf("%d\n",&n);
	f=1;
	j=1;
	sum=0;
	for(i=1;i<=n;i++){
		item=f*1.0/j;
		sum=sum+item;
		f=-f;
		j=j+2;
	}
	printf("sum=%f\n",sum);
return 0;
}